The invention relates to full time transmission of digital signals over a high capacity channel and it finds a particularly important application in transmission over channels having characteristics provided for direct broadcasting by satellite, at a carrier frequency of 12 GHZ allowing a digital flow rate of 20 Mbits per second.
Cable ground networds on the other hand only offer a passband of about 14 MHz, instead of the 27 MHz of a satellite channel, which means that full time multiplexing, if it has characteristics allowing transmission thereof over a cable network and reception with the same apparatus whatever the transmission channel, fails to fully use the satellite transmission capacity.
Satellite broadcasting in Europe will use the MAC/PACKET as described "The EBU C-MAC/PACKET system for Direct Broadcasting by Satellite" by H. Mertens et al in "links for the future" Science, Systems and Services for Communications, IEEE, Elsevier science Publisher BV, (Netherlands), 1984, pp. 3-8. This system is based on the sequential transmission of luminance and chrominance signals in analog form with time compression, and packet multiplexing for the sound and the data. Among the variations of MAC/PACKET, D2 MAC/PACKET uses, for the digital signals, a duobinary type modulation, with a passband compatible with that of ground cable networks, whereas C-MAC/PACKET uses 2-4 PSK coding for the digital signals, with a very wide pass band.
A description of the D2-MAC/PACKET may be found in French patent application No. 84 08727.